Current technology utilizes many types of sensors for detecting components, analytes, in numerous types of fluids. For example, some of these range from oxygen sensors for detecting oxygen in air for control of the air and fuel ratio for combustion in internal combustion engines to multiple phase sequential analyzers for qualitative and/or quantitative measurement of constituents or analytes of blood. For instance, the measurement of blood gases, usually a measure of the partial pressures of oxygen and carbon dioxide, along with the pH from a sample of arterial blood gives the state of the acid base balance or the effectiveness of both the respiratory and cardiovascular systems of the human or vertebrate body. These various types of sensors can be prepared by various techniques including layered circuit or integrated circuit technologies, as for example, thick film, thin film, plating, pressurized laminating and photolithographic etching, and other like silk screening processes.
Many of these sensors require some form of preparation before they are ready for use in measuring analytes in samples. If the thick film sensors have an electrolyte that is substantially aqueous, the membrane of the sensor would probably need hydrating prior to use. This situation would arise when the analysis equipment is started or when a sensor in the equipment is changed. The hydration process would be time consuming for performance on the equipment and would probably be performed in a separate operation prior to installation in the equipment. Also the sensors are usually calibrated prior to measuring analyte in samples by passing reference samples with known values of analytes by the sensors. If improper results are obtained the integrity of the sensor may be a question. The integrity of a sensor may even be a question for a sensor that is newly installed in the equipment so that diagnostic testing might be in order upon such an installation.
In addition to the use of sensors in stationary analysis equipment, portable analysis equipment is being developed which place additional demands on the sensors. For instance, technology has developed portable analysis devices that can shorten or overcome transporting the samples to stationary equipment which can be burdensome and in some instances deleterious to the accuracy of the results of the measurements. For measuring constituents of blood, the blood sample is drawn from the patient and usually, as in the case of blood gases, transported to a central location for testing. There are many reports in the literature that suggest that the values obtained in the measurement of blood gases depend on the type of measuring equipment and the technique for sample collection.
To overcome this problem technology has been developed to eliminate this transportation operation as much as possible so that a patient's blood gases could be measured at the bedside in a manner similar to measuring a patient's temperature U.S. Pat. Nos. 3,000,805 and 3,497,442 show two such devices. The former has sensors located on a syringe plunger and the latter has sensors placed on the syringe well to conduct the measurements. In the allowed United States patent application Ser. No. 07/343,234, Applicants assignee describes and claims a portable blood gas sensor which includes sensors fabricated from a conventional silk screening process where the sensors are screened on to a ceramic substance. Typically these sensors have electrodes used in conjunction with an electrolyte and with an analyte permeable membrane that covers the sensor. These portable sensors still should be calibrated like the stationary equipment so one or more of the reference fluids can be used with these portable devices.
It is an object of the present invention to provide a sensor in a ready-to-use state for stationary analysis equipment and especially in a ready-to-use state for a portable analysis device to make such a device more user friendly and actually more portable,